Thyroid cancer at a glance
- Thyroid cancer is an abnormal malignant cell growth in the thyroid gland.
- The thyroid, a butterfly-shaped gland that sits just in front of the wind pipe, produces important hormones that regulate key functions such as metabolism.
- Symptoms of thyroid cancer include a lump in the neck, localized pain and difficulty swallowing or breathing.
- The cause of thyroid cancer is not known, but women are three times more likely to get it than men.
- Early life exposure to radiation and certain genetic conditions also increase risk of thyroid cancer.
- Papillary and follicular are the two most common types of thyroid cancer and both are usually treatable if caught early.
- Surgery and radioiodine therapy are the most common treatments.
What is thyroid cancer?
Thyroid cancer occurs when malignant (abnormal) cells grow out of control in the tissues of the thyroid gland. The thyroid is a butterfly-shaped gland located near the trachea, or windpipe. It has two lobes that flank both sides of the throat, giving it its distinctive butterfly shape. The thyroid is responsible for producing hormones that regulate metabolism, pulse rate, blood pressure and body temperature.
According to the National Institutes of Health, thyroid cancer is the ninth most common cancer in the United States, and the rate of diagnosis has increased rapidly over the last few decades. Some of this increase can be attributed to improved methods of detection. Women are three times more likely than men to get thyroid cancer. The reason for this is unclear but women are also more susceptible to most all thyroid conditions.
Most patients diagnosed with thyroid cancer are between the ages of 25 and 65. It appears earlier in women, generally in their 40s and 50s, and later in men, around their 60s and 70s.
Thyroid cancer is considered to be highly treatable, and the survival rate of depends largely upon the age of the affected individual and what stage the cancer is in upon discovery. Five year survival rates for thyroid cancer discovered in stages I and II are near 100 percent, but survival rates do vary based on the types of thyroid cancers.
Types of thyroid cancer
- Papillary carcinoma accounts for 80 percent of thyroid cancer diagnoses, making it the most common type by far. This cancer can develop on one or both lobes of the gland and is usually slow growing. It may spread to nearby lymph nodes, but it tends to have a good prognosis (high rate of successful treatment and survivability).
- Follicular carcinoma is seen in 10 percent of cases and is slightly more aggressive than papillary. Follicular thyroid cancer is found more often in nations where diets are deficient in iodine, a trace mineral found in certain vegetables and seafood. Unlike the papillary type, follicular thyroid cancer usually does not spread to lymph nodes, but instead to other organs such as the lungs. The prognosis for follicular thyroid cancer is still good in most cases, but it may be more difficult to treat if it has spread to other organs before it is discovered.
- Hürthle cell carcinoma is a subtype of follicular carcinoma and is sometimes referred to as oxyphil cell carcinoma. It accounts for roughly 3 percent of diagnosed cases. This cancer behaves similarly to follicular carcinoma, but the cells have a distinctive appearance that differentiates them as their own sub-variety. This type is seen more frequently in older patients.
- Medullary carcinoma originates from parafollicular cells in the thyroid. Parafollicular cells are also called C cells because they are responsible for producing a hormone called calcitonin. Because of this, medullary carcinoma is sometimes discovered when elevated levels of calcitonin are detected in blood tests. Approximately 4 percent of diagnosed cases fall under this category. The medullary subtype is more likely to spread to surrounding lymph nodes and organs, and can be more difficult to treat than papillary and follicular carcinomas.
- Anaplastic carcinoma is a rare and highly aggressive form of thyroid cancer seen in approximately 2 percent of diagnosed cases. The cells found in anaplastic cancers differ starkly from normal thyroid cells, making this a particularly difficult and complicated subtype to treat.
Symptoms and signs of thyroid cancer
People experiencing any of the following symptoms should see their doctor for follow-up. While these may be signs of thyroid cancer, they may also be caused by some other condition requiring attention. Symptoms of thyroid cancer include:
- A lump or nodule felt on the neck near the throat (lumps in the thyroid are not unusual and most often benign)
- Difficulty swallowing
- Pain in the throat or neck
- Swollen lymph nodes in the neck
- Breathing problems
- Persistent cough
- Changes in the voice such as hoarseness
Causes and risk factors
Thyroid cancer does not have a known cause, but certain risk factors have been identified. These include:
- Childhood radiation exposure (particularly in the head and neck)
- Family history of thyroid cancer, goiter (enlargement of the thyroid) and/or certain DNA abnormalities that are linked with the disease
- Gender, as thyroid cancers occur three times more often in women, who tend to develop the cancer at an earlier age than men
- Radioactive fallout exposure
- Low consumption of dietary iodine (less common in the U.S.)
Thyroid cancer treatment
Treatment of thyroid cancer varies based on the type of cancer and how far the disease has progressed. In many cases, multiple treatment approaches are used simultaneously. The more common types of thyroid cancers tend to respond better to surgery and radioiodine therapy.
Surgery is the primary method used to treat thyroid cancers. This may involve the removal of a single thyroid lobe (called a lobectomy) or the removal of the entire thyroid gland (a thyroidectomy). Thyroidectomy patients and some lobectomy patients will need to take medication to compensate for the loss of hormones once naturally produced by the gland.
Surgical treatment of thyroid cancer may sometimes involve the removal of lymph nodes that have been affected by the cancer.
Radioactive iodine therapy
Radioactive iodine (radioiodine) therapy is a targeted radiation treatment specifically for thyroid cancers. Since the thyroid gland absorbs most of the iodine consumed in our diets, introducing radioactive iodine via capsule or liquid directs a concentrated dose of radiation to the thyroid cells. Sometimes this treatment is used as a follow-up to surgery to destroy any thyroid tissue that could not be surgically removed.
Thyroid hormone therapy is prescribed after a thyroidectomy and may also be employed to stop the cancer from spreading. Cancer patients are administered doses of thyroid hormones that are higher than the body’s normal levels, and this causes the pituitary gland to produce less TSH (thyroid stimulating hormone). This reduction in TSH is thought to slow the rate of cell growth – including cancer cell growth – within the thyroid.
External beam radiation therapy
External beam radiation therapy uses a machine to direct a concentrated beam of radiation that slows cancerous cell growth. This method is used more frequently in medically complex and/or aggressive cases such as medullary and anaplastic carcinomas.
Chemotherapy is a regimen of anti-cancer drugs administered orally or via injection. In most cases, chemotherapy is not an effective method for treating thyroid cancers, but it may be used in conjunction with external beam radiation therapy in cases that are more advanced such as anaplastic carcinoma.
Targeted therapy medications may also be used in certain cases where surgery and radioiodine treatments are ineffective. Targeted therapy involves cutting-edge, orally-administered drugs that focus specifically on attacking cancer cells and inhibiting their growth.